The present invention relates to an image forming method using a photosensitive and pressure-sensitive (hereinafter sometimes simply "sensitive") material incorporating microcapsules containing a photosensitive composition. Particularly, the invention relates to a method of removing sag in the exposure portion of such photosensitive and pressure-sensitive material during image formation, and a method for positional control of the photosensitive and pressure-sensitive material during image formation.
Examples of photosensitive and pressure-sensitive materials employing microcapsules containing a photosensitive composition, a system having a support which carries thereon synthetic-high-molecular-resin-walled capsules containing a vinyl compound, a photopolymerization initiator, and a colorant precursor are disclosed in commonly assigned Japanese Unexamined Patent Publication No. 57-179836. In an image recording method using such a system, the microcapsules are hardened in the form of an image by an exposure process, and the not-hardened microcapsules are broken by pressure to release a colorant precursor to thereby obtain a color image. The method has the advantage that a high quality image can be obtained with a dry-type simple treatment. However, the method has the disadvantage that this system is inferior in photosensitivity to a system using silver halide.
A recording material having an improved photosensitivity such that a high quality image can be obtained with a drytype simple treatment has been disclosed in commonly assigned Japanese Unexamined Patent Publication No. 61-275742. The disclosed recording material includes a support on which at least photosensitive silver halide, a reducing agent, a polymerizable compound and a color image forming matter are applied. The polymerizable compound and the color image forming matter are enclosed in the same microcapsules as a photosensitive compound.
An image forming method in which this photosensitive and pressure-sensitive material is used to form an image has been disclosed in commonly assigned Japanese Unexamined Patent Publication No. 61-278849. According to that image forming method, a latent image is formed by imaging exposure. Then, development is carried out by heating so that a part of the polymerizable compound in portions containing a latent image is polymerized to produce in those portions a high molecular compound to thereby harden the microcapsules. Next, pressure is exerted on the material while it is superposed on an image-receiving material having an image-receiving layer to which the color image forming matter can be transferred so that at least part of other microcapsules located out of the portion containing the latent image are ruptured to transfer the color image forming matter to the image-receiving material to thereby obtain a picture image on the image-receiving material.
As an example, an image forming apparatus using the aforementioned photosensitive and pressure-sensitive material and automatically performing the above-described procedures (of forming a latent image on the photosensitive and pressure-sensitive material through exposure, carrying out development by heating, and applying pressure to the material superposed on an image-receiving material to obtain a picture image on the image-receiving material) is disclosed in Japanese Patent Application No. 60-287492.
An exposure section and an exposure method according to the apparatus and method of the type described above are as follows:
FIG. 1 shows an image forming apparatus to which the present invention can be applied. In FIG. 1, a glass plate 3 carrying an original placed upside down moves in the directions of an arrow A.
An illuminating lamp 8 and a mirror 6 are provided under the glass plate 2 to illuminate the original. Further, a fiber-optics lens array 10 is provided under the glass plate 3 to form an image of the original on a photosensitive and pressure-sensitive material S at a predetermined exposure position.
A cartridge 14 containing a roll 12 of the photosensitive and pressure-sensitive material S is removably attached to a side of a housing 1. A pair of draw-out rollers 21 and 22 housed in a magazine connection dark box 20 are disposed at the exit 16 of the photosensitive and pressure-sensitive material S from the cartridge 14 so that the material S wound on the roll 12 can be drawn out in segments of a predetermined length or pulled back into the cartridge 14 if occasion demands.
When the forward end of the photosensitive and pressure-sensitive material S advances to the pair of rollers 21 and 22, the rollers 21 and 22 are moved apart to thereby facilitate the advancing of the material S. A cutter unit 23 for cutting the material S is disposed in front of the magazine connection dark box 20. (The term "front" as used herein means downstream with respect to the advancing direction of the photosensitive and pressure-sensitive material S). The cutter unit 23 is followed by a guide plate 24.
An exposed material supporting roller 26 and a pair of nip rollers 28 and 30 in forced contact with the roller 26 are disposed in front of the guide plate 24. The material S, guided by the guide plate 24, is brought into contact with the exposed material supporting roller 26 by the pair of nip rollers 28 and 30, and then the material S at a middle position between the nip rollers 28 and 30 is exposed to light carrying an image of the original through the fiberoptics lens array 10.
A thermal developing device 40 for thermally developing the exposed sensitive material S is disposed in front of the exposed sensitive material supporting roller 26. After being heated to about 120.degree. C. to develop it with the thermal developing device 40, the photosensitive and pressure-sensitive material S is passed through a vertical guide device 58 to a superposing device 70 and there superposed on an image-receiving paper C fed from an image-receiving paper cartridge 73. A pressure of about 500 kg/cm.sup.2 is applied to the superposed material S by a transfer device 88 to transfer a picture image to the image-receiving paper. The photosensitive and pressure-sensitive material S, which is then spent, is then separated from the image-receiving paper C having the image formed thereon by a peel-off device 90 and then discarded.
However, since a thin material is used a support in the photosensitive and pressure-sensitive material, the material curls easily. Accordingly, as shown in FIG. 2, in the case where the material S entering at the exposure entrance-side nip roller 28 is nipped by the exit-side nip roller 30, with the forward end of the material S being in a curled state, the material 32 at the exposure position tends to float up from the exposure roller. This of course interferes with proper image formation, causing a focusing error during image exposure.
Moreover, in the aforementioned apparatus, the standby position of the photosensitive and pressure-sensitive material S prior to exposure is located between the draw-out rollers 21 and 22, that is, just after the material exits from the cartridge, whereas the operating position of the material S is at the position of the cutter unit 23.
When a copy start key is pushed, exposure can be started only after the photosensitive and pressure-sensitive material S has been transported from the standby position to the exposure position. Accordingly, the time required for duplicating each sheet is undesirably long.